MUOS began providing legacy satellite communications after the first satellite was launched in 2012.

The four main and one spare satellites have a dual-capability, with both legacy Ultra High Frequency Follow-on (UFO) capabilities and a replacement Wideband Code Division Multiple Access (WCDMA) system that will have 10 times the communications capacity.

This double capacity is meant to maintain the legacy narrowband communications for DoD while the more advanced MUOS capability came on-line. The newer WCDMA adapts commercial cellular technology to let warfighters communicate beyond-line-of-sight.

“‘MUOS’ acceptance for operational use is an important milestone for the Navy, and it's one step closer for significant communications improvements for all our forces,” Rear Adm. Carl Chebi, commander of Program Executive Office (PEO) for Command, Control, Communications, Computers and Intelligence and PEO Space Systems, said in a statement.

Narrowband communications is used by all the combatant commands, ships, many aircrafts, and ground forces on several warfighting applications.

MUOS’ WCDMA capability previously entered a combatant command restricted operations phase in July 2016. That allowed early adopters to gain experience using the system. More recent Navy Expeditionary Combat Command and Marine Corps field exercises helped refine the concept of operations development and usage, the Navy said.

“The feedback we've received from the first WCDMA users has been invaluable. That was the real dividend of this phase: working out some kinks but also gaining insight for concepts of operations that we didn't envision even a few years ago,” Capt. Chris DeSena, program manager for the Navy Communications Satellite Program Office, which oversees MUOS, said.

The WCDMA capability lets users work beyond-line-of-sight and transmit simultaneous voice, video, and mission data on a system connected to military network, but the main impediment to faster MUOS usage is the scarcity of newer MUOS-enabled radios.

In June, Marine Corps officials said they would become the first service to use MUOS for the battlefield as it looks to widely install the system in its radios by the fall (Defense Daily, June 6).

The Marine Corps has already fielded many Harris [HRS] MUOS-ready AN/PRC-117G manpack radios and is working to update the firmware to best use the WCDMA waveform.

The service expects to start initial MUOS fielding in the fourth quarter of 2018 and then achieve initial operational capability (IOC) by the first quarter of 2019.

The Navy said it expects the MUOS system to be declared fully operational after a Multi-Service Test and Evaluation in summer 2019.